1. Field of the Invention
The invention relates to a method for fitting an optical fiber into an end fitting, the end fitting obtained in this way constituting a device for connecting to another connecting device incorporating an optical fiber. It also relates to any connecting assembly containing such an end fitting and, in particular, an optoelectronic connector.
2. Description of the Prior Art
Optical fibers used for long distance telecommunications (several dozen kilometers) and with a high information flow (more than 500 megabits/second for one kilometer) are fibers with a core smaller than 0.070 mm (70 microns).
The tendency to use optical fibers with a very small diameter is justified by the theory of the transmission of the light wave in the fiber. In addition, the reduction in the diameter has an economic significance, because the smaller the fiber diameter the greater the fiber length which can be drawn from a preform with standard dimensions. It is known that the length of fiber drawn from a given preform is inversely proportional to the square of the diameter of the said fiber. It is important to obtain maximum optical fiber lengths in order to limit the number of connections by splicing (adhesion or welding) or by removable connectors.
In the telecommunications field the admissible losses on a homogeneous fiber length containing no connection is below 10 and sometimes below 0.5 dB/km. The insertion loss introduced by a connection should only very slightly exceed the order of magnitude of the theoretical losses, i.e. 0.2 dB. Such a result assumes that it has been possible to bring about the almost perfect alignment of the cores of the fibers to be connected, after polishing or splitting the faces to be joined end to end and moving them into abutting relationship, whilst only leaving a negligible air layer thickness.
The practical realisation of such a connection necessitates the production of a mechanical hollow support which surrounds and fixes in place the end of the optical fiber. This support constitutes or forms part of a more or less complicated connecting device permitting abutting of the mechanical supports located around the ends of the two fibers to be connected.
The mechanical support or end fitting of each fiber materializes a reference surface, which is for example the lateral surface or given portions thereof on the periphery of a cylindrical or frustum-shaped body. This reference surface defines the position of the optical fiber, which must, for example, be accurately positioned in accordance with the axis of the cylinder or the frustum. In practice the fiber core has a diameter of approximately 1/10 mm (100.mu.), whilst the diameter of the end fitting of the abutting face is several dozen times larger. The positioning of the optical fiber in the end fitting requires the use of complex precision equipment. The very nature of the fiber and in particular its fragility leads to the presence of relatively flexible protective means adding to the complexity of the problem referred to hereinbefore.